Flexible collapsible fluid container and method of producing same



Ju y 1943. A. N. SPANEL 2,323,629

FLEXIBLE COLLAPSIBLE FLUID CONTAINER AND METHOD 0F PRODUCING SAME Filed Dec. 16, 1942 4 Sheets-Sheet 1 v N V II, llllllllllllill'll'lli l y 4 A. N. SPANEL 2,323,629

FLEXIBLE COLLAPSIBLE FLUID CONTAINER AND METHOD OF PRODUCING SAME Filed Dec. 16, 1942 4 Sheets-Sheet 2 uwml MW v

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FLEXIBLE COLLAPSIBLE FLUID CONTAINER AND METHOD OF PRODUCING SAME Filed Dec. 16, 1942 4 Sheets-Sheet I5 IINVENITOR. I AB /a HA MNSPANEL ATTORNEYS July 6, 1943.

A. N. SPANEL 2,323,629

FLEXIBLE COLLAPSIBLE FLUID CONTAINER AND METHOD 0 PRODUCING sAME Filed Dec. 16; 1942 4 Sheets-Sheet 4 47 I QINVENTOR.

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4 ATTORNEKS Patented July 6, 1943 UNITED \STATES PATENT OFFICE FLEXIBLE COLLAPSIBLE FLUID CONTAINER AND METHOD OF PRODUCING SAME Abraham N. Spanel, New York, N. Y.

Application December 16, 1942, Serial No. 469,268

11 Claims.

This invention relates to flexible, collapsible fluid containers and method of producing same. The invention is particularly adapted for and may be usefully employed in the making of inflatable articles, such as toys, life-saving equipment, pontoons and the like; as well as liquid containers, such as canteens and larger receptacles for holding and transporting liquids.

An object of the invention is to provide flexible collapsible fluid containers adapted to be fabricated from sheet material so as to provide a light but strong structure, and the method of producing the same.

Another object of the invention is to provide such a device having a body entirely closed except for filling and emptying means.

The invention consists in the novel features, arrangements and combination of parts embodied by way of example in the method and apparatus hereinafter described as illustrating the preferred form of the invention, and the invention will be more particularly pointed out in the appended claims.

Further objects, features and advantages of the invention will more clearly appeal from the detailed description given below taken in connection with the accompanying drawings which form a part of the specification.

Referring to the drawings:

Fig. 1 is a plan view of a sheet from which a container, such as a bladder, may be made;

Fig. 2 is an end elevational view showing the sheet folded (somewhat enlarged) with its oppositely extending free edges sealed together and with a filling tube secured to a side wall;

Fig. 3 is a plan view showing a further stage of manufacture wherein the side seams have been added to complete the structure;

Fig. 4 is a somewhat enlarged sectional view taken at 4-4 of Fig. 3, showing further details of the end seam;

Fig. 5 is a somewhat enlarged sectional view taken at 55 of Fig. 3, showing further details of the side seam;

Fig. 6 is a sectional view taken at 66 of Fig. 3 showing further details of the attachment of the filling tube to the wall structure;

Fig. 7 is a partial sectional view showing a modified means of attaching the said tube;

Fig. 8 is a plan view of a portion of the structure shown in Fig. 6, illustrating further the closure means for said tube;

Fig. 9 is an elevational view of the filling tube held in closed position by the closure means;

Fig. 10 is a sectional view taken at I0--l0 of Fig. 9;

Fig. 11 is a cross-sectional View illustrating a modified form of the side seam arrangements;

Fig. 12 is a plan view of a sheet representing the inner wall member of a modified form of container or bladder structure;

Fig. 13 is a plan view of a sheet representing a reinforcing layer of said modified form;

Fig. 14 is a plan view illustrating said completed modified structure;

Fig. 15 is a somewhat enlarged sectional view taken at l5-l5 of Fig. 14;

Fig. 16 is a somewhat enlarged sectional view taken at |6l6 of Fig, 14;

Fig. 17 is a side elevational view of a container adapted especially for liquids and comprising in addition to a bladder an outer carrying casing;

Fig. 18 is a plan view of the device of Fig. 17;

Fig. 19 is a somewhat enlarged sectional view taken at 19-49 of Fig. 1'7, and shows the posi-- tion of the bladder seam (of Fig. 16) within the casing;

Fig. 20 is a somewhat enlarged sectional view taken at 2020 of Fig. 17, and shows the position of the end seam; and

Fig. 21 is a somewhat enlarged sectional view showing details of construction of a modified form of filling tube especially adapted for liquid and preferable for containers for holding liquid.

An important feature of the invention is the use of thermoplastic material in the form of relatively thin flexible sheets, and the manner in which the fluid-holding bladder may be fabricated from such sheets while at the same time providing dependable seals at the seams which additionally are reinforced; and also the provision of suitable fllling means for said bladder.

Certain features disclosed but not claimed herein form the subject matter of my copending application Serial No. 486,031, for fFlexible collapsible fluid bladders," filed May 7, 1943.

In Fig. 1, the unfolded sheet is designated as I and represents a sheet of flexible thermoplastic material, the thickness of which I have found to be preferaly .004"-.O16". I have found that thermoplastic synthetic resinous material, such as vinyl resins, have given entirely satisfactory results, and according to the embodiments of the invention to be referred to herein, will be described in connection with such sheet material made from vinylite. Other suitable thermoplastic resinous materials, such as vinyl butyrol, ethyl cellulose glycolate, Saran, and the like thermoplastic materials, may be similarly employed.

The sheet I is provided with a. hole 2 through wh ch a filling tube designated in general as 3 (Fig. 2) is inserted. The filling tube 3 (Fig. 6) comprises an upper tubular portion 4 and a lower flange portion 5. The filling tube i preferably inserted through the hole 2 before the sheet is folded about the fold lines 6-'| and 89 (Fig. 1) to provide an upper fold l0 and a lower fold ll (Fig. 2). In this embodiment, the filling tube is made of rubber and the upper and lower portions of the flange are coated with a suitable adhesive, preferably in the form of synthetic rubber cement, such as Hycar." An annular disk I2 (Fig. 6) made of thermoplastic sheet material, such as the material of which sheet I is made, is positioned over the tubular neck 4 with its lower face cemented to the upper face of flange 5, and an annular disk I3, made of relatively stronger fibrous material such as fabric, is similarly cemented to the lower face of flange 5 with its central opening in register with the opening in the filling tube 3. The disk I3 extends beyond the flange 5 so as to provide an extending marginal edge. the upper surface of which is coated with thermo-active material, such as liquid vinylite. After the disks I2 and I3 have been thus attached to the flange 5, the tubular portion 4 i passed downwardly through the hole 2 (Fig. 1) to bring the upper face of disk I2 and the upper marginal face of disk I3 into engagement with the inner face of the sheet corresponding to the fold l0. Heat and pressure are supplied to cause the sheet I to be fused to the upper face of disk I2 and to the thermo-active surface of the marginal upper surface of disk I3, thereby providing two independent seals between the sheet and filling tube. The temperature which I have successfully employed with the vinylite material in effecting fusion is 240 F.260 F. for a period of 35-40 seconds at a pressure sufiicient to seal the parts together; which pressure is of the general order of the molding pressure, which for vinylite" is 12001800 pounds per square inch.

In Fig. 7, I have shown a somewhat modified means of attaching the filling tube to the sheet material. The flange is designated as 5', and instead of having its upper and lower surfaces coated with synthetic rubber, the entire flange is dipped in liquid vinylite so as to provide an enveloping layer I4 which surrounds the lower portion of the tubular portion 4' and completely encloses the flange 5', except for the lower opening therethrough. In this embodiment, the entire upper face of the fibrous disk I3 is coated with a thermoplastic material, which under pressure and heat fuses to the coating I4 and to the inner face of the sheet I' overlying the marginal edge of disk I3. In this embodiment, the thermoplastic disk I2 may be employed, or, in the alternative, the sheet I may be directly fused to the coating I4.

Preferably after the filling tube 3 has been inserted in place, the right-hand edge of sheet I (Fig. 1) is folded to the left about the fold line 8-5 and the left-hand portion of the sheet is folded to the right about the fold line 6'I so that the marginal oppositely disposed edges I5 and I6 overlap (Fig. 11) and provide an inner juncture II. A strip of fibrous material I8, such as fabric whose upper surface has been provided with a coating of thermo-active material such as vinylite" I9, is inserted between the fold I0 and II with the face I9 engaging the inner faces of the sheet material on respectively opposite sides of the juncture line I! so as to lie over the and overlying the same.

of the fold I0 overlying the strip I8 and to the corresponding oppositely disposed lower face of the fold II. During the sealing operation, the heat and pressur usually causes a small amount of the coating I9 to penetrate through the fabric strip I9 with the resulting tendency of the inner face of the fabric to slightly stick to the inner face of the fold I l, and similarly there is a tendency for the inner face of fold I0 adjacent the marginal edges of the strip I8 to stick to the corresponding portions of the inner face of the lower fold II. Accordingly, upon release of the heat and pressure applying means, such as clamps, and before the thermoplastic material has substantially hardened, these inner surfaces which have slightly adhered are separated, as by runn ng the operator's hand between the folds I0 and I I down to the adjacent edge of the envelope.

After the end seam has been completed, a fabric strip 2i (Fig. 5), similarly coated with a thermo-active layer 22, is creased intermediate its edges so as to provide a V-strip and this V-strip is inserted between the overlapping free edges on one side of the envelope so as to extend the full length thereof, with the point of the V facing outwardly and inwardly from the edge of the folds I0 and II so as to provide marginal edges 23 and 24 extending beyond the point of the V which will then be disposed in overlapping relationship with the juncture point 25. Heat and pressure clamps are similarly positioned on opposite sides of the envelop extending throughout the length of the edges and overlying the full width of the V-strip and the marginal edges 23-24, and heat and pressure applied to seal the marginal edges 23-24 together and to seal the fabric V-strip 2I to the inner faces of the envelope on opposite sides of the said first seal Similarly, by manual manipulation, the folds I0 and II, including the sides of the V-strip, are separated so that when the bladder is filled with fluid, the seam assumes the position indicated in broken lines in Fig. 5.

The respectively opposite side seam is similarly formed, except that in this instance there is no means of access to the interior of the bladder for manually manipulating the folds to separate them when they have become stuck together adjacent the seam. I have found that with respect to this last scam, the folds may be separated in the following manner. While the clamps are still in position, or immediately after they have been removed, I introduce air into the bladder through the filling tube 3 in an amount only sufficient to very slightly inflate the bladder, and close the tube 3; then before substantial hardening of the heat-softened thermoplastic has taken place, by pressing down on the bladder, as by the hands of the operator, and forcing the air toward the said last seam, sufficient pressure Is created to separate the folds adjacent the seam.

I have provided the following means for closing the filling tube which provides a sturdy dependable structure which may be readily manufactured and attached to the filling tube with facility so as to always be available for quickly opening or closing the tube.

Referring to Figs. 6 and 8: A fibrous strap 26 made of suitabl material such as heavy fabric strip, is passed around the tubular portion 4 and folded back upon itself and secured in place such as by a rivet 21 which preferably is formed as a part of one fastening element 28 (Fig. 8). The opposite or free end of the strap is provided with a cooperating fastening means 28 which is preferably secured thereto by a rivet portion 30 passing through a folded portion of the strap which projects beyond the fastening portion 23 t provide an engageable tab 3|. When it is desired to close the filling tube, the tubular portion is collapsed and sealed by being bent over upon itself so as to provide two substantially parallel legs. The strap 26 is wrapped around the two legs and the fastening means 21-29 are pressed into engagement (Fig. which securely holds the tube in closed position completely sealing the same.

Fig. 11 shows a modified form of seam in which the 'folds l0 and H have their superimposed marginal edges 23', 24' folded over against the outer face of one of the folds, such as I l; and the V fabric strip 2| is provided with an inner surface layer of thermo-active material and the sides of the V extend substantially beyond the marginal edges 23 and 24. From this, it will be seen that upon the application of heat and pressure the first seal is formed between the corresponding inner faces of the folds |0-| I; a second seal is formed between the respectively adjacent faces of the marginal edges 23'24'; the other face of the marginal edge 23' is sealed to the outer face of fold H and similarly the other face of the marginal edge 24' is sealed to the inner face of the strip 2| which is also sealed along one leg to the outer face of fold H and along the other leg to the outer face of fold H).

In Figs. 12-46 inclusive, I have shown a modified form of structure in which 32 designates a sheet of thin flexible thermoplastic sheet material, such as vinylite, which is provided with a central opening 33 through which the neck of a filling tube is passed and secured to the sheet in the manner previously described. A sheet 34 of relatively stronger fibrous material, such as fabric (Fig. 13) is provided with a corresponding opening 35 and on one face is provided with a thermoactive coating 36 extending peripherally to provide a marginal coated area on one side of said sheet. The sheet 34 is superimposed over the sheet 32 with the marginal coating 36 lying adjacent the inner face of sheet 32 and with the filling tube extending through the hole 35. The sheet is then folded substantially about its central axis in the position designated in Figs. 14 and 15, and V-strips treated in the manner previously described, designated 31, 38 and 39, and preferably mitered at respectively adjacent ends, serving to reinforce the seams in the manner previously described, and the seal thus efiected is otherwise similar to that shown in Fig. 5 previously described with the exception that in this embodiment, in addition to the inner wall formed of the sheet of thermoplastic material 32, there is an outer fold (Fig. 16) or wall formed of the fabric material 34, which outer wall closely encloses the inner wall but is preferably unattached thereto, except for a marginal area. The marginal area of the fabric thus secured intimately to th inner thermoplastic layer 32 extends from the outer edges 4|] for a substantial distance inwardly and preferably to the inner edge 4| of the V-strips. In this embodiment, the seams corresponding to two of the strips, such as 31 and 38, may be manually manipulated with the hand as previously described to separate the inner folds where they stick adjacent the seams, and the other seam may be manipulated with air pressure as previously,

described.

Instead of merely supplying the coating along the marginal edge as at 36, it has been found,

of the fabric strip, and this does not materially affect the steps of manufacture of the ultimate product since the clamps are limited in their surface engagement and hence the major area inwardly of the seam areas is unaffected and the outer and inner layers are not cemented except at and immediately adjacent the-clamps.

The embodiment of Figs. 1-5 inclusive presents a structure which, while capable of sustaining reasonable pressure, is nevertheless not adapted for rough handling and the thermoplastic material is subject to abrasion without some form of covering. The embodiment shown in Figs. 12 to 16 inclusive provides a much more durable structure in view of the fabric coating 34. However, it is preferable that a relatively heavy casing be provided. In Figs. 17-20, I have disclosed a bladder, such as one of those previously described, provided with a carrying case designated 42, made of relatively heavy fibrous material such as duck or canvas, and preferably provided with suitable carrying means such as handles 43. This outer casing is entirely separate from the inner bladder and is of a size somewhat smaller than the size of the bladder in order to prevent undue stretching of the bladder. The casing is preferably entirely enclosed except for a hole through which the neck of the filling tube, such as 3, extends, and except for the means of inserting the bladder within the casing; since it would be inconvenient to sew the bladder within the casing in view of the danger of perforating the bladder. As a means f inserting the bladder within the casing, I have provided a relatively narrow slot or opening 44 disposed between the filling tube opening and an adjacent edge of the casing with a flap closure 45 to close the opening 44 after the bladder has been inserted. I find this preferable to sewing the casing closed after the bladder has been inserted and also preferable to providing a releasable closure extending throughout a greater area of the casing.

I have devised a somewhat modified form of filling spout which is especially desirable where the containers are to be used for liquid. This structure is shown in section in Fig. 21, and in this embodiment illustrates the structure of the form disclosed in Figs. 12-16 inclusive, having an integrally attached outer fabric layer. Referring to Fig. 21, the inner or thermoplastic layer is designated as 32, the fabric layer as 34' and the outer casing 42. In this embodiment, th filling tube 46 is formed of molded thermoplastic material, such as vinylite, and is provided with a lower flange portion 41, which is thermoplastically sealed to the inner layer 32 as at 48, and the ply 32' may be also sealed to the corresponding area of the outer layer 34' by a.v thermo-active coating as at the corresponding area designated 49. A reinforcing fabric disk 50 is sealed to the lower face of the flange 41 and the outwardly disposed marginal area of the vinylite wall 32' in the manner fully described heretofore. A rigid outer sleeve Si is disposed exteriorly of the tubular portion 46 and a rigid inner sleeve 52 is disposed interiorly of the tube 46. These sleeves are preferably made of relatively rigid plastic material, but may be made of metal if desired. The inner diameter of the sleeve 5| and the outer diameter of the sleeve 52 are preferably such as to cause the liquid seal between the tube 46 and sleeve 5|, and the sleeves are preferably held against outward movement by means of a bead 53 integrally formed on the outer end of the tubular portion 46. This bead additionally serves as a sealing ring to engage the closure cap 54 which is suitably removably secured to the sleeve 5| as by cooperating threaded portions 55-56 formed respectively on the sleeve and cap. In the alternative, the bead 53 may be omitted and the sleeves may be otherwise secured to the thermoplastic tube 46 as by friction and/or cement; in which case the tube 48 still preferably extends upwardly to facilitate sealing engagement with the cap. For example, the outer sleeve 5i may be provided with an interior which is tapered from its bottom end upwardly and outwardly toward its upper end, and

the outer diameter of the inner sleeve 52 may be correspondingly tapered; so that when the tube 46 is positioned between the tapered walls of the shells, the locking of the tube into position will be facilitated.

In containers of the character described adapted to carry liquid, I have found that the thickness of .004"-.008" is desirable for the thermoplastic sheet material of which the bladder is fabricated; since this permits the blader to "crawl" and pennits better conformation for a given shape of bladder to the enclosed casing.

While I have described the V seam (Fig. 5) in its preferable condition, as one in which the inner faces of the fabric strip are not adhered one to the other, and while this has been found to give the best results; nevertheless the inner faces of the V fabric strip may be cemented or otherwise adhered.

It is also within the contemplation of the invention that, instead of starting with a plain sheet of material I (Fig. 1) and folding the same upon itself by means of a seem as disclosed in Fig. 4, the thermoplastic material may be initially made in tubular form without a seam, in th general form in which sausage casings are made, and the filling tube inserted through one wall of the tubular structure which has been cut to the desired length; and the bladder completed by the mere insertion of the two oppositely disposed V seams such as shown in Fig. 5 and referred to as end seams.

With respect to Fig. 1'7, it is noted that where the inner bladder in such a structure is of the type shown in Figs. 1-3 inclusive, in which the wall is unprotected by afibrous outer layer (as in Figs. 12-16), the thin wall under certain conditions is subject to abrasion from a rough surface interior of the casing or from foreign particles which may gain access to the casing. For this reason, the type of bladder having the fabric or other suitable outer layer (as in Figs. 12-16) is preferable in certain instances, as'where liquid is to be carried and relatively hard usage results.

Further, I have found that with a bladder smaller than the casing 42 (as is usual practice with rubber and the like inflatable bladders) this does not give nearly such strength as when the bladder is larger than the casing. By this I mean that the volumetric size of the casing in its extended form when in use must be less than the volumetric size of the bladder when distended but before its side walls have been stretched. To express it in another way, the inside dimensions of the casing 42 should be such that the disiension of the bladder will not permit appreciable stretching of the thermoplastic material, especially adjacent the seams (see Figs. 19 and 20). This is especially desirable with the bladders of the type of Fig. 3.

Having thus described my invention with particularity with reference to the preferred form of the same and in connection with the preferred method of producing the same, and having referred to certain modifications, it will be obvious to those skilled in the art, after understanding my invention, that other changes and modifications may be made therein without departing from the spirit and scope of my invention, and I aim in the appended claims to cover such changes and modifications as are within the scope of the invention.

What I claim is:

1. A bladder comprising opposite walls of flexible thermoplastic resinous sheet material whose adjacent marginal edges are fused together in overlapping relationship providing self seams of said material, and a reinforcing strip extending over an edge of said seam. said strip having an inner thermoplastic face fused to said sheet walls on respectively opposite sides of said seam edge.

2. A bladder comprising opposite walls of flexible thermoplastic resinous sheet material whose adjacent marginal edges are fused together in overlapping relationship providing self seams of said material, and a reinforcing strip extending over an edge of said seam, said strip having an inner thermoplastic face fused to said sheet walls on respectively opposite sides of said seam edge, said strip having an opposite non-thermo-active ace.

3. A bladder comprising opposite walls of flexible thermoplastic resinous sheet material whose adjacent marginal edges are fused together in overlapping relationship providing self seams of said material, and a reinforcing fabric strip extending over an edge of said seam, said strip having an adherent thermo-active coating on its face adjacent said seam fused to said sheet walls on respectively opposite sides of said seam edge.

4. A bladder comprising a single sheetof flexible thermoplastic material folded upon itself about a first fold line to provide two superimposed layers, one of the layers extending beyond the other and being folded back upon itself'about a second fold line with its adjacent marginal edge overlapping the oppositely extending corresponding marginal edge of the other layer and secured thereto by a fused seal, a fabric strip disposed between said layers and overlying said seam with one face adhered to the respectively oppositely extending sheet ends, two marginal edges of one layer extending between and transverse said fold lines being secured to the respectively corresponding marginal edges of the other layer by fused seals to provide oppositely disposed seams, and fabric strips folded along respective longitudinal lines to provide respective V-sections disposed between said layers with the fabric fold lines positioned against said seams and the outer faces of said V-strips lying against and being united with the inner faces of said layers.

5. The method of forming a bladder which comprises overlapping marginal edges of respectively cooperating free ends of flexible sheet thermoplastic resinous material, placing a fabric strip at the juncture so provided and with one face of said strip lying contiguous corresponding faces of said ends on respectively opposite sides of said juncture, there being a thermo-active substance on said contiguous face of said strip and applying heat and pressure to said overlapped edges and to said fabric strip to thereby cause said overlapped marginal edges of sheet material to be fused into a sealing seam and said fabric strip to be adhesively fused to said sheet material bridging said seam.

6. The method of forming a bladder which comprises overlapping marginal edges of respeclapped edges and fabric strip to tively cooperating free ends of flexible sheet thermoplastic resinous material, placing a fabric strip at the juncture so provided and with one face of said strip lying continguous corresponding faces of said ends on respectively opposite sides of said juncture, there being a thermoactive substance on said contiguous face of said strip and applying heat and pressure to said overthereby simultaneously cause said overlapped marginal edges of sheet material to be fused into a sealing seam and said fabric strip to be fused to said sheet material bridging said seam.

'I. The method of forming a bladder which comprises folding a flexible sheet of thermoplastic resinous material upon itself in loop formation so that two of its oppositely extending edges overlap, inserting within said folded sheet and overlying said overlapped edges a fabric strip having a surface coatingof thermo-active material on a face adjacent said overlapped edges and in engagement with respective of said sheet ends, applying heat and pressure to said overlapped edges and to said fabric strip to cause fusion between said edges and adhesion between said sheet ends and said fabric, to thereby provide an envelope with open ends, thereafter inserting V fabric strips within said envelope with the open sides facing toward each other and with the closed edge of the V disposed adjacent to and inwardly spaced from respective edges of said open ends of said envelope, whereby the pairs of edges of said open ends extend beyond respective of said V-strips to provide respective superimposed marginal edges, said strips being coated on their outer faces with a thermo-active material, applying heat and pressure to said extended marginal edges and said respectively adjacent V- fabric strips simultaneously to thereby cause fusion between the respective superimposed marginal edges disposed outwardly beyond said V- strIps and adhesion between said V-strips and sheet inwardly of said marginal edges.

8. The method of fabricating a fluid-container bladder provided with a filling opening and having walls of flexible thermoplastic resinous material which comprises, forming a partially enclosed envelope having one seam portion unsealed so as to permit access to the interior thereof, ap-

plying heat and pressure to overlapping portions l of said seam portion and fusing said seam portion to thereby provide a seal closing the envelope, removing said heat and pressure after said fusion sealing, looselyinfiating said bladder with air or the like inflating medium through said fllling opening prior to substantial hardening of said thermoplastic material and manually manipulating the bladder from the exterior to force said inflating medium toward said seam portion and causing said medium to separate stuck portions of said bladder wall contiguous said seam portion prior to the substantial hardening of said thermoplastic material.

9. In the method of forming a bladder from relatively thin flexiblethermoplastic material for containing fluid, the steps which comprise placing correspondingly opposite side walls of said material one over the other and arranging the free marginal edges of one side wall in superimposed relation with the corresponding marginal edges of the other side wall, placing corresponding walls of fabric exteriorly of said thermoplastic walls with the free edges of the fabric walls lying contiguous respectively corresponding edges of said thermoplastic wall, the free marginal edges of said fabric wall being provided with an inner face of thermo-active material, applying heat and pressure to said superimposed marginal edges of said thermoplastic and fabric walls sufficient to fuse respectively adjacent faces of said thermoplastic walls together and to fuse the inner faces of said fabric walls to the correspondingly adjacent faces of said thermoplastic walls along said marginal edges.

10. The method of fabricating a bladder for containing a fluid, which comprises placing a sheet of relatively thin flexible thermoplastic material in superimposed relation to a corresponding sheet of fabric of substantially the same size with the free marginal edges of said fabric sheet having a thermo-active face adjacent the thermoplastic sheet, folding the laminated ply thus formed so as to bring the free marginal edges of the upper and lower folds of said laminated ply into overlapping relation, placing fabric strips of V formation between said folds with the points of said respective V-strips directed outwardly and spaced inwardly of the respective edges of said folds to provide a border beyond the V-strips, said V-strips having their outer faces provided with a thermo-active surface, applying heat and pressure to substantially the area defined by said border area and by the area of said V-strips, to thereby seal said V-strips to the inner faces of said thermoplastic ply and seal said inner ply folds together outwardly beyond said V-strips and seal said fabric ply along the zone of its said marginal edges to the corresponding area of said thermoplastic ply.

11. The method of fabricating a fluid-container bladder provided with a filling opening, which comprises overlapping marginal edges of respectively cooperating free ends of flexible sheet thermoplastic resinous material, placing strip fabric at the juncture so provided for a portion of the peripheral extent thereof and with one face of said strip lying contiguous corresponding faces of said ends on respectively opposite sides of said juncture, said continguous face of said strip being coated with a thermo-active substance, applying heat and pressure to said overlapped edges and to said fabric strip to thereby cause said overlapped marginal edges of sheet material to be fused into a sealing seam and said fabric strip to be adhesively fused to said sheet material bridging said seam, to thereby provide a partially enclosed envelope having a seam portion unsealed so as to permit access to the interior of said envelope, applying heat and pressure to overlapping portions of said unsealed seam portion and fusing said seam portion to thereby provide a seal closing the envelope, removing said heat and pressure after said fusion sealing, loosely inflating said bladder with an in fiating medium through said filling opening prior to substantial hardening of said thermoplastic material and manually manipulating the bladder from the exterior to force saidinflating medium toward said seam portion and causing said medium to separate stuck portions of said bladder wall contiguous said seam portion prior to the iulblstlantial hardening of said thermoplastic ma- ABRAHAM N. SPANEL. 

